1. Structure of an Atom

2. Symbol
Charge
Mass
Where is it located?
Proton
Neutron
Electron

3. Nucleus Composed of protons and neutrons
responsible for most of the mass of the atom
Composed of protons and neutrons
Protons
Symbol = p+
Charge = +1
Mass = 1 amu
Neutrons
Symbol = n0
Charge = 0

4. responsible for most of the volume of the atom
Electrons
responsible for most of the volume of the atom
Found in energy levels
Symbol = e-
Charge = -1
Mass = 0 amu

5. How are the protons, neutrons, and electrons arranged in the atom?
What does each color represent?
Green
Red
Yellow + - + +

6. Why was John Dalton’s Theory wrong?
Discovery of isotopes!

7. Isotopes Do they have the same number of protons?
Kind of like twins…alike, but different
Isotopes are the same elements, but they have different masses due to different numbers of neutrons!
Do they have the same number of protons?
What about protons and neutrons?
Protons == Neutrons

8. Examples of ISOTOPES

9. 35Cl 37Cl Protons Neutrons 17 17 protons 18 neutrons 17 17 protons

10. Protons
Neutrons 1H 2H 1 3H 1
= Protons
= Neutrons

11. Isotopic Notation – how we write isotopes
Mass Number X A B
Element Symbol
Atomic Number 12 6 C

12. Isotopic Word Notation – how we write isotopes12 6 C
Element name – mass number
Example:
Carbon – or C - 14

13. Determining P, N, and E
Atomic Number – The number of protons in an atom.
In a neutral atom: Number of protons = number of electrons
Mass Number = protons + neutrons
******Mass number is NOT THE SAME as AVERAGE atomic mass************
# of Neutrons = mass number – protons
Average Atomic Mass: decimal number calculated on period table

14. Practice 14Si 28 18Ar 38 Element Name Isotopic Notation Atomic Number
Mass Number
Protons
Neutrons
Electrons
Avg. Atomic Mass
Nitrogen – 14 12 13
14Si 18 22
18Ar 28 38